I want to sort my list descended but when I use the keyword .sort I get an error:

This is not a record, so it has no fields to access!
106| { model | teams = List.sort.map (\p -> {p | activated = True}) model.teams, activatedOutput = True}
^^^^^^^^^
This `sort` value is a:
List comparable -> List comparable
But I need a record with a map field!

This is the line I have modified and with which I want to sort the list.

sort is not a keyword, it is a function that takes a list of comparable items and returns a new list of the sorted comparable items. You can’t combine it like that with the List.map function.
What you can do is to create a pipeline of functions that each use take and return a List, like{ model | teams = model.teams |> List.sort |> List.map (\p -> {p | activated = True}) }.

This wont like that directly, because your teams List contains records, which are not comparable. There is List.sortBy to the rescue, see https://package.elm-lang.org/packages/elm/core/latest/List#sortBy
You would use it in pipeline style like that{ model | teams = model.teams |> List.sortBy (\p -> tooSomeComparableValue p) |> List.map (\p -> {p | activated = True}) }.